This application claims the priority of 198 26 170.5-53, filed Jun. 13, 1998, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a method for influencing machine background noise which at least from a rotating part of the machine, and especially for influencing the background noise within a passenger compartment of a motor vehicle. The amplitudes and/or the frequencies of primary vibrations which cause the background noise are changed, preferably lessened and/or supplemented, as well as a shaft, the axis of rotation of the rotating part being disposed coaxially with the axis of rotation of the bearing, and with a radial adjustability for changing the mounting conditions of the rotating part in and on the shaft bearing.
Machines having rotating parts usually have at least one type of particularly disturbing background noise. One reason for this disturbing noise is due to the fact that, among others, the rotating parts, especially shafts, induce vibrations in other components. To transfer vibrations between components or for the introduction of vibrations from one component into another component, resonant frequencies are important. The mathematical connection of this frequency-related transfer is called xe2x80x9ctransfer function.xe2x80x9d
U.S. Pat. No. 5,332,061 discloses a method for suppressing vibrations applied to the car body and a corresponding vehicle. The applied vibrations in question, which among other things also lead to audible vibrations, originate from the motor and are transferred at the points where the motor is fastened to the body. To damp these vibrations the vehicle has shakers, i.e., mechanical vibration exciters which are disposed in the area of at least some points of connection of the motor with the body. When the motor is operated, the shakers are excited according to the motor""s rotatory speed, opposite in phase to the vibrations coming from the motor, thereby at least damping the transfer of the introduced vibrations. The corresponding frequencies and amplitudes thereof for the secondary vibrations are in this case taken from a previously determined data chart.
U.S. Pat. No. 5,434,783 discloses a vehicle in which the noise background that is audible within the vehicle is affected by sound waves. In addition to normal loudspeakers, a piezo element is also used to excite the body to vibration at least in areas and thereby influences it to emit sound waves; i.e., the piezo element acts like the coil of a loudspeaker, while the body constitutes the vibrating diaphragm. With the previously known process and the previously known apparatus an improvement of the subjective impression is achieved within the passenger compartment.
A farther-reaching embodiment of the above development for influencing the subjectively perceived riding perception is disclosed in DE 195 31 402 A1. In accordance with a parameter, and in this case especially the motor speed and/or the velocity, not only the airborne sound but also the body sound and vibrations perceived by the body are influenced. For this purpose, data determined according to the magnitude of the parameter certain data are read out of a data field and converted with the aid of vibration exciters to secondary vibrations also perceivable by the body. By these measures, in conjunction with the affecting of the acoustically perceived airborne sound, both positive and negative interferences with the artificial secondary vibrations are produced by the primary vibrations forming at the motor vehicle end when the vehicle is operated. The interferences can, as desired, diminish the perceived impression, or else replace it with a certain impression, such as a shift in a vehicle provided with a stepless drive.
An object of the present invention is to produce a method and apparatus by which perceptible vibrations of a machine having rotating parts can be reduced.
This object has been achieved according to the present invention by a method in which the mounting conditions between the shaft bearing and a rotating part, especially a shaft of the machine, held for rotation in the shaft bearing is controllably varied. By varying the mounting conditions, the transfer function of the vibrations is varied, especially the vibrations producing the sound waves between the rotating part and the shaft bearing or a component in contact with the shaft bearing and by a shaft bearing the radial adjustability has a piezoelectrically active material. Through the radial adjustment unit, the effective radial stretching in the area of the rotating part to be mounted and/or the contact pressure on the rotating part is controlledly reversibly variable at least between two dimensions. By the targeted and reversible variation of the radial extent of a radial adjusting unit having especially piezo elements, or of the pressure applied radially to the rotating part, the mounting conditions of the shaft can be varied during operation by a targeted action from without.
Variation of the shaft mounting conditions brings about, for example, a change of the values of the natural vibrations of the rotating part and also the transfer function from the rotating part to another component. By changing the transfer function, the propagation of vibrations, i.e., the transferable energy, which comes from the rotating part to another component is varied, especially it is at least diminished.
In a radial adjustment unit, the engagement is performed by applying an electric voltage. This leads to a variation of the resonance frequencies and natural frequencies of the rotating part, and also to a change in the transfer and transmission of vibrations.
Also, in the manner mentioned, free play which varies due to temperature influences, for example, can occur while the rotating part is rotating. This is useful, for example, in compensating for play. This is useful preferably in the case of a crankshaft and/or camshaft as a rotating part of an internal combustion engine, particularly a diesel or gasoline motor, since the introduced vibrations, and especially the emission of sound within a passenger compartment of a vehicle driven by an internal combustion motor, can be influenced.
A use for the method and/or the apparatus of the present invention is expedient for rotating parts of electric motors, especially rotors, but also in aircraft engines, for example jet engines or propellers.
In a currently preferred manner, the use of the invention is desirable also for a crankshaft and/or camshaft of an internal combustion engine, preferably a diesel or gas engine, since then the introduced vibrations and especially the emission of sound thereby within a passenger compartment of an internal combustion engine-driven motor vehicle can be influenced. Preferably here the influence of the noise level perceived as especially annoying by the driver of a vehicle and coming at least in part from the motor is performed at the place where it develops and, not as has long been common, only at the place where it is perceived by the driver. In this manner, the expense involved in the electronic controls and accessory apparatus (microphone, loudspeaker and the like) is reduced.